My question will be introduced at the end of this post. I have thought on this question for some time now. But first off let me say that I do not know all there is to know about the theory of Solipsism. From what I gather, the definition can be summed up in the phrase:
The theory that only the self exists, or can be proved to exist.
Holding this to be true, person A kills himself. Moments before doing so, he scribbles down on a sheet of paper:
If You can read this when I am dead, the theory of Solipsism is false.
This seems to be a great way to find out if the theory of Solipsism is true or not, but I have come up with a counter:
Person B discovers person A's body and the note. If Person A kills himself, having written down what he did, then he would have only been acting in person B's perception of the world; hence, the theory of Solipsism would be true to person B, because person B can still only be sure of his own existence- and cannot be sure that person A ever did exist.
This brings up yet...